The fifth annual Metropolitan Horticulture Show will open at Tysons Corner Shopping Center near McLean on Thursday, Aug. 4. The event is sponsored by county and city extension agents representing Maryland, Virginia and the District of Columbia. It is open to the public each day, Thursday through Saturday, Aug, 4, 5, and 6, from 10 a.m. to 9:30 p.m.

Extension horticulture specialists will be on hand to conduct the ever-popular Sick Plant Clinic, which provides individual free consultation service on plant maladies. For diagnosis of a problem, Richard Biggs, Montgomery County Extension Horticulture agent, recommends bringing an entire plant if the plant is small. Otherwise, bring as large a sample as you can spare from the affected portion of a large plant; it should be a live piece representative of the plant's condition.

In addition to the Sick Clinic, there will be demonstrations and talks on a variety of topics of interests to indoor gardeners, including indoor plants for low light areas, insects on houseplants, introduction to light gardening, bonsai, and orchids.

Lawns and outdoor gardens, too, will have their share of attention.

The show will feature more than 30 commercial and educational exhibits. Cooperating groups include the Professional Grounds Management Society, National Capital Parks, University of Maryland, Virginia Polytechnic Institute and State University, and the University of the District of Columbia.